#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main()
{
	int cost = 1;
	int money = 0;
	int quality = 0;
	int sum = 0;
	scanf("%d", &money);
	quality = money / cost;
	sum = quality / 2;
	sum = sum + money;
	printf("%d", sum);



	return 0;
}